I think one of his best showings was retconned...wasn't his defeat of Darkseid retconned with the 'Desaad is impersonating DS' thing?

Versions have had awesome showings though, and other versions I'd put as clear underdogs to Strange in a straight magical combat. So I'd say they range from a peer in terms of magical ability to underdog.

I also don't quite know where to rank his strength and durability...it doesn't seem to come into play as much as Loki's, but we know its there...I'm assuming he's not as durable as Loki, but I could be wrong...

So, in general, with him being a rough peer to Strange magically, somewhere between Strange and Loki, but maybe on the lower end toward Strange, because while he won't have the lowest lows of Strange, he hasn't punched in the highest weight class quite as often, and one of the times he did I believe was retconned (though he still has some other REALLY awesome showings).

Lower versions equal to strange, best versions on par with Loki, and generally somewhere in between...

Fate as a Lord of Order would have more "natural power" thsan either Strange/Loki, has real durability factor, but Strange seems to be able to call upon His higher powers better...